Dimmable Single-Stage Power Converter Adaptive Frequency Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dimmable single-stage power converters fail to achieve deep dimming with good accuracy and are plagued by audible noise, while maintaining a high power factor and low total harmonic distortion (THD).
Innovation Solution
A dimmable single-stage power converter with adaptive switching frequency control, operating in pulse width modulation (PWM) mode at varying frequencies from 90 kHz to 25 kHz, and transitioning to skip mode to mitigate noise and distortion, allowing deep dimming down to 1% with improved THD and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the switching frequency is kept high in dimmable single-stage power converters, then the power factor and THD are maintained, but audible noise is generated and deep dimming accuracy cannot be achieved
Solution Approach 1:
The patent implements dynamic switching frequency adjustment where the frequency changes based on the dimming level. At high dimming levels, a higher frequency (e.g., 65 kHz) is used to maintain power factor and THD performance. As dimming level decreases, the frequency is reduced (e.g., to 20 kHz) to eliminate audible noise and enable accurate deep dimming control. This dynamic adaptation resolves the contradiction between maintaining power quality and achieving deep dimming accuracy without noise.
Solution Approach 2:
The patent changes the switching frequency parameter as a function of dimming level. By adjusting this critical parameter dynamically, the system optimizes performance across different operating conditions. The frequency is set to specific values (e.g., 65 kHz at high dimming, 20 kHz at low dimming) to simultaneously satisfy multiple requirements: power factor correction, THD limits, audible noise elimination, and dimming accuracy.
2Object-affected harmful factors
If the switching frequency is reduced to mitigate audible noise, then noise is reduced, but power factor and THD performance deteriorate
Solution Approach 1:
The system dynamically adjusts switching frequency based on operating conditions. Rather than using a fixed low frequency that would compromise power factor and THD, the frequency is elevated (e.g., to 65 kHz) when power quality is critical. This dynamic behavior ensures that power factor and THD performance are maintained while still enabling noise mitigation when dimming levels require lower frequencies.
Solution Approach 2:
The patent employs periodic switching at frequencies specifically chosen to avoid audible ranges while maintaining power quality. By operating at frequencies like 65 kHz during periods when power factor and THD are prioritized, and switching to 20 kHz when noise mitigation is needed, the system achieves both goals through time-varying periodic action.
3Adaptability or versatility
If deep dimming is implemented with fixed switching frequency, then dimming range is extended, but dimming accuracy and noise control are compromised
Solution Approach 1:
The patent implements dynamic switching frequency adjustment that adapts to dimming level requirements. For deep dimming applications, the frequency is reduced (e.g., to 20 kHz) to enable accurate control at low power levels while eliminating audible noise. For higher dimming levels, the frequency increases (e.g., to 65 kHz) to maintain power quality. This dynamic adaptation enables the full dimming range (e.g., 1% to 100%) to be achieved with both accuracy and noise control.
Data Source
AI summary
Systems, methods, and apparatus for a circuit with adaptive switching frequency control are disclosed. The method comprises operating a controller of the dimmable single-stage power converter in pulse width modulation (PWM) mode at a first switching frequency level from a maximum dimming duty-ratio level until a first dimming duty-ratio level. The method further comprises operating the controller in PWM mode, while reducing switching frequency from the first switching frequency level to a second switching frequency level, from the first dimming duty-ratio level until a second dimming duty-ratio level. Also, the method comprises operating the controller in PWM mode at the second switching frequency level from the second dimming duty-ratio level until a current command (Vipk) falls below a predetermined low limit value. Further, the method comprises operating the controller in skip mode, while reducing the switching frequency from the second switching frequency level, until a minimum dimming duty-ratio level.